Fixes #5 Don't install when primary database is not available

Author: reidmorrison

lib/active_record_replica/active_record_replica.rb

@@ -18,6 +18,13 @@ def self.install!(adapter_class = nil, environment = nil)
       return
     end
 
+    # When the DBMS is not available, an exception (e.g. PG::ConnectionBad) is raised
+    active_db_connection = ActiveRecord::Base.connection.active? rescue false
+    unless active_db_connection
+      ActiveRecord::Base.logger.info("ActiveRecord not connected so not installing ActiveRecordReplica")
+      return
+    end
+
     version = ActiveRecordReplica::VERSION
     ActiveRecord::Base.logger.info("ActiveRecordReplica.install! v#{version} Establishing connection to replica database")
     Replica.establish_connection(replica_config)